Nedbank not adhering to customer preferred debit order date

I have a xredit facility with Nedbank and on a monthly basis they chose to deduct the debit order on the 23rd and not on the 25th as specified when i took the facility. This is an inconvenience as i constantly getting threatening emails about being reported to the credit bearau and get told my insurance on the credit facility will lapse as a result of non payment as if i did not specify on the application what my preferred debit order date is and when i receive my salary. This happens on a monthly basis and i believe its totally unacceptable and is totally bad customer experience.